Expansion joint for road sections



June 13, 1967 A. BOSCH! 32 9 I EXPANSION JOINT FOR ROAD SECTIONS Filed June 1, 1965 2 Sheets-Sheet 1 June 13, 1967 A. BOSCH! 7 3,324,774

EXPANSION JOINT FOR ROAD SECTIONS Filed June 1, 1965 2 Sheets-Sheet 2 United States Patent 3,324,774 EXPANSION JOINT FOR ROAD SECTIONS Antonio Boschi, Milan, Italy, assignor to Societa Applicazioni Gamma Antivibranti SAGA S.p.A., Milan, Italy Filed June 1, 1965, Ser. No. 460,160 Claims priority, application Italy, Apr. 21, 1965,

8,744/65 8 Claims. (Cl. 94-18) ABSTRACT OF THE DISCLOSURE An expansion joint covering an expansion gap between adjacent road sections, comprises a strip of elastomeric material bridging the gap. The strip has a substantially planar upper face providing continuity of the road surface, a substantially planar lower face resting on end portions of the road sections and downwardly projecting beads depending from the longitudinal edges of the strip and anchored in the respective road sections. A pair of grooves in the lower face of the strip adjacent the beads substantially prevents strata of the strip adjacent the lower face from being compressed by strip-compressing thrust applied to longitudinal edges of the strip upon expansion of at least one of the road sections. The lower face of the strip is also formed with a series of mutually parallel grooves extending obliquely between the longitudinal grooves and having convexly curved bottom surfaces. Preferably the upper face of the strip is formed with a series of grooves which are in register with corresponding grooves of the series formed in the lower face and have concavely curved bottom surfaces so that each pair of registering grooves defines in the strip a downwardly arched partition of the elastomeric material.

This invention relates to road-building techniques. More specifically, the invention relates to expansion joints covering an expansion gap between two adjacent road sections, said gap being directed transversely of the road axis and being of a width which is variable due to longitudinal thermal expansion of at least one of said sections.

The term road section as used herein primarily includes a road-surfaced bay of a bridge. Since such a bay usually defines an expansion gap in conjunction with either a subsequent bay or a road length built on dry land, it is to be understood that such a road length will also be considered a section. Another example of a pair of road sections comprising at least one thermally expand able section is found in roads or highways composed of a sequence of large concrete slabs cast in situ, wherein, as to the thermal expansion, each slab behaves as a bay of a bridge and requires an expansion gap adjacent at least one of its ends.

The most common disadvantage of known expansion joints for road sections is that, as the gap betWeen the sections becomes narrower due to thermal expansion of a section, the material or member covering the gap bulges upwardly thereby forming a rib which breaks the longitudinal continuity of the otherwise smooth road surface. It will be readily realized that the presence of such ribs, extending transversely of the road, is not only disturbing but also dangerous, depending on the extent to which the ribs protrude from the surface of the road, because of jolts produced on passing vehicles.

A primary object of this invention is to provide a no bulge expansion joint for road sections.

Another object of the invention is to provide a no bulge joint comprising a strip of rubber bridging the expansion gap, wherein thermal expansion of one or both road sec- 'ice tions will develop in the strip a system of forces maintaining the upper surface of the strip at least substantially flush with the surfaces of said sections.

Still another object, ancillary to the above-stated objects, is to provide a joint structure capable of being prefabricated in part and subsequently easily put in place Without requiring particular skill.

Further objects and advantages of the invention will appear from the following description, in which reference is made to the accompanying drawings wherein:

FIGURE 1 is a side view partly in section showing a pair of consecutive bays of a road bridge including an expansion joint;

FIGURE 2 is an enlarged sectional view showing the details of an expansion joint in accordance with the invention;

FIGURE 3 is a cross-sectional view taken substantially' on line HIIII of FIG. 2;

FIGURE 4 is a fragmentary plan view on line IV-IV of FIGURE 2;

FIGURE 5 is a cross-sectional view on line VV of FIGURE 4;

FIGURE 6 is a detail view of FIG. 2 at an intermediate stage of assembly of the joint;

The general arrangement shown in FIG. 1 comprises a pair of consecutive road sections or bays 21, 22 having their adjacent end portions supported by a common pier 23 through the interposition of supports 24, 24 permitting the bays to thermally expand in their longitudinal directions. The supports 24, 24 are advantageously of the character disclosed by British patent specification No. 601,157 assigned to the assignees of this application.

Each of the bays 21, 22 essentially consists of a solid monolithic slab of reinforced concrete having a road covering 25 on its upper surface, said covering advantageously consisting of a bituminous conglomerate having a thickness s (FIG. 2) of about 4-5 cm. The bays are separated from each other by an expansion gap 26, extending tranversely of the road axis and bridged by an expansion joint generically denoted 30 in FIG. 1. The function of the expansion joint 30 is to assure continuity of the road surface irrespective of variations in the width of the expansion gap 26 caused by ambient temperature variations, without causing the passing vehicles to jump on crossing the gap.

The joint essentially comprises a fiat strip 27 of solid resilient rubber (PEG. 2) extending along the gap 26, i.e. extending perpendicularly to the plane of FIG. 2. The strip 27 bridges the gap 26 and comprises a lower face 28 superposed on the bays 21, 22, and an exposed upper face 29 flush with the surface of the road. The strip 27 also has a pair of planar fianks 27A, 27B, each forming a dihedral angle of about 100 with the upper face 29 of the strip. Moreover, two depending longitudinal flange or beads 31, 31 are integrally moulded with the strip 27 at the opposite longitudinal edges of the latter for fastening the strip to its supporting structure. Each of the beads is formed with a continuous longitudinal slit 32 (FIG. 6) in a plane substantially perpendicular to the faces 28, 29, said slit comprising a cylindrically enlarged bottom portion 33 of circular cross-sectional shape, whereby the bead is in effect comprised of a pair of cheeks which are separated from each other by said slit and have lateral faces 34, 35, respectively, parallel to the slit.

The free longitudinal edge (undersurface) of the bead, on which the slit 32 opens, is formed at regular intervals with notches 36 (FIG. 3) extending tranversely to the slit and crossing the latter without cutting into the enlarged bottom portion 33 of the slit.

A metal blade 37, including a beaded longitudinal edge 38 complementary to the bottom portion 33, is inserted into the slit 32 to extend through the entire length of the strip 27 while protruding downwardly below the lower surface of the angle irons bead 31. Two 39, 39 embrace the checks of the bead and are pressed against the lateral faces 34, 35 by means of bolts 40, whereby the head 31 is clamped on the beaded part of the blade 37. Each of the bolts 40 passes through corresponding apertures formed both in the angle irons and blade in register with a notch 36 in the bead 31. In the tightened condition of the bolts, the edge of the lower wing of each of the two angle irons abuts the blade 37 and is advantageously spotwelded thereto at suitable intervals. Finally, the lower edge portion of the blade 37 has bolted thereto by means of bolts 42 a plurality of longitudinally spaced anchoring tabs 41 (FIG. 3) each consisting of a short piece of angle iron having one of its wings secured to the blade by a bolt 42.

In assembled condition, both of the beads 31, blades 37, clamping irons 39 and anchoring tabs 41 are embeded in the concrete material of the respective bays or road sections 21, 22, as can be seen in the left-hand part of FIG. 2; Whereas the right-hand part of FIG. 2 shows the manner in which this is done in practice.

More specifically, preliminarily to the installation of the rubber strip 27 with its metal armatures 37, 39, 41, the mutually facing end portions of the bays 21, 22 are each formed to present a threshold 50 adjacent the gap 26 and a channel 51 separating the threshold 50 from the remaining upper surface of the bay. Both the threshold and channel extend transversely to the length of the bay and the threshold comprises a substantially planar upper face 50'. The depth of the channel 51 with respect to the face 50' is somewhat greater than the overall distance H (FIG. 6) by which the beads 31 with the metal armatures project downwardly with respect to the lower face 28 of the strip 27. In these conditions, once the strip 27 has been pre-assembled with its metal armatures, it can be superposed on the thresholds of the two bays, with its face 28 supported by the upper faces 50' of the thresholds, so that the expansion gap 25 is bridged by the strip. Subsequently, each of the channels 51 is filled with concrete or cement mortar up to the line 52 (FIG. 2). Upon setting of the filling, the bays are surfaced by coating thereon a sub-layer 25A and the wearing-layer 25, according to the conventional practice. It will be seen in FIG. 2. that the layers 25 bear against the flanks 27A, 27B of the rubber strip 27 and that the thickness of the latter is substantially equal to the thickness s of said layers (about 4-5 cm), according to optimal conditions for carrying out this invention. It is to be understood, however, that greater thickness values can be adopted for the strip 27 in the case of particularly heavy-trafiic routes or runways. In such a case, the level of the upper faces 50' of the thresholds 50 shall be correspondingly lowered with respect to the exposed surface of the layers 25.

An important aspect of this invention resides in certain details of the strip 27.

More specifically, it will be seen in FIGURES 4, 5 and 6 that a series of parallel grooves 43, 44 is formed in the faces 28 and 29, respectively, of the strip. The grooves form an angle of 40 to 50 with the longitudinal axis of the strip, each of the grooves 44 in the upper face 29 being in register with a groove 43 in the lower face 28. Moreover, the bottom of each of the upper grooves 44 (FIG. 5) is concave, whereas the bottom of each groove 43 in the lower face 28 is correspondingly convex. -In this manner each pair of companion-grooves 43, 44 defines in the body of the strip 27 a partition 45 forming an inverted arch (in the architectural sense); the thickness of said partition advantageously amounts to A to /2 thickness of the strip. It will be also seen in FIG. 4 that the grooves span a substantial part of the width of the strip, leaving free a pair of longitudinal marginal portions 27c, 27d, having each a width advantageously amounting to 2025% of the width of the strip.

Moreover, a continuous longitudinal groove 46 is formed in the lower face 28 of the strip at a location adjacent the root of each of the beads 31 (see FIG. 6); the depth of said groove is at least /5 thickness of the strip and preferably amounts to A1 to /3 said thickness. Each of the oblique grooves 43 in the lower face 28 extends from a groove 46 to the other groove 46 in said face.

It has been found in practice that the above-described system of grooves provides an excellent means automatically preventing the strip from arching upwardly when the gap 26 becomes narrower due to thermal expansion of a bay. Actually, as one of the bays starts expanding towards the other bay, a bending moment is obviously applied to the strip by its two beads approaching each other, so that the strip would apparently have a tendency to bow upwardly over its supporting thresholds and gap 26. However, it appears that, at the same time, the wearing-layers 25, 25 apply to the flanks 27A, 27B of the strip a system of compressive forces directed parallel to the road surface, and it also appears that the presence of the grooves 46 at the root of the beads 31 substantially prevents said forces from compressing the strata of the strip adjacent the lower face 28 of the latter while permitting them to compress the strata adjacent the upper face 29, thereby to counteract the bending moment mentioned herein-before, so that the strip appears to be merely compressed transversely to its length without bowing. The compression of the strip 27 primarily affects the downwardly arched partitions 45, each of which, flexes downwardly, i.e. towards the upper faces 50 of the thresholds 50, thereby both preventing the strip from increasing its thickness and concurring in maintaining the strip in its fiat condition.

It is evident, however, that the explanation set forth above is merely theoretical and should not be interpreted as a limitation of this invention, while, on the other hand, expansion joints constructed according to this invention have actually been found in practice to remain flush with the road surface notwithstanding ambient temperature variations of about 70 C.

What I claim is:

1. An expansion joint structure comprising: a pair of road sections having a road surface and adjacent end portions enclosing therebetween an expansion gap; a flat strip of elastomeric material superposed on said end portions to bridge by its width both said end portions and gap; said strip comprising a substantially planar upper face providing for the continuity of the road surface over said gap, a substantially planar lower face in strip-supporting contact with said end portions of said sections, and a pair of integral beads depending from the longitudinal edges of the strip embedded and anchored in the respective road sections, said longitudinal edges receiving a stripcompressing thrust from the respective road sections on thermal expansion of at least one of said sections; and said lower face of the strip being formed with a pair of grooves directed longitudinally of the strip and adjacent the respective beads whereby the strata of the strip adjacent said lower faoe are substantially prevented from being compressed by said thrust, and being moreover formed with a series of mutually parallel grooves extending obliquely between said pair of longitudinally directed grooves, the grooves of said series having each a convexely curved bottom surface.

2. An expansion joint structure comprising: a pair of road sections having a road surface and adjacent end portions enclosing therebetween an expansion gap; a flat strip of elastomeric material superposed on said end portions to bridge by its width both said end portions and gap; said strip comprising a substantially planar upper face providing for the continuity of the road surface over said gap, a substantially planar lower face in stripsupporting contact with said end portions of said sections, and a pair of integral beads depending from the longitudinal edges of the strip embedded and anchored in the respective road sections, said longitudinal edges receiving a strip-compressing thrust from the respective road sections on thermal expansion of at least one of said sections; said lower face of the strip being formed with a pair of grooves directed longitudinally of the strip and adjacent the respective beads whereby the strata of the strip adjacent said lower face are substantially prevented from being compressed by said thrust, and being moreover formed with a series of mutually parallel grooves extending obliquely between said pair of longitudinally directed grooves, the grooves of said series having each a convexly curved bottom surface; and said upper face of the strip being also formed with a series of grooves which are in register with corresponding grooves of the series formed in the lower face and have each a concavely curved bottom surface, whereby each pair of registering grooves defines in the strip a downwardly arched partition of said elastomeric material.

3. An expansion joint structure comprising: a pair of road sections having a road surface and adjacent end portions enclosing therebetween an expansion gap; a flat strip of elastomeric material superposed on said end sections to bridge by its width both said end portions and gap; said strip comprising a substantially planar upper face providing for the continuity of the road surface over said gap, a substantially planar lower face in strip-supporting contact with said end portions of said sections, and a pair of integral beads depending from the longitudinal edges of the strip embedded and anchored in the respective road sections, said longitudinal edges receiving a strip-compressing thrust from the respective road sections on thermal expansion of at least one of said sections; said lower face of the strip being formed with a pair of grooves directed longitudinally of the strip and adjacent the respective beads whereby the strata of the strip adjacent said lower face are substantially prevented from being compressed by said thrust, and being moreover formed with a series of mutually parallel grooves extending obliquely between said pair of longitudinally directed grooves, the grooves of said series having each a convexly curved bottom surface; and said upper face of the strip being also formed with a series of grooves which are in register with corresponding grooves of the series formed in the lower face and have each a concavely curved bottom surface, whereby each pair of registering grooves defines in the strip a downwardly arched partition of said elastomeric material, said partition having a thickness amounting to A to /2 of the thickness of the strip.

4. An expansion joint structure comprising: a pair of road sections having a road surface and adjacent end portions enclosing therebetween an expansion gap; a flat strip of elastomeric material superposed on said end portions to bridge by its width both said end portions and gap; said strip comprising a substantally planar upper face providing for the continuity of the road surface over said gap, a substantially planar lower face in strip-supporting contact with said end portions of said sections, and a pair of integral beads depending from the longitudinal edges of the strip embedded and anchored in the respective road sections, said longitudinal edges receiving a strip-compressing thrust from the respective road sections on thermal expansion of at least one of said sections; said lower face of the strip being formed with a pair of grooves directed longitudinally of the strip and adjacent the respective beads whereby the strata of the strip adjacent said lower face are substantially prevented from being compressed by said thrust, and being moreover formed with a series of mutually parallel grooves extending obliquely between said pair of longitudinally directed grooves, the grooves of said series having each a convexly curved bottom surface; and said upper face of the strip being also formed with a series of grooves which are in register with corresponding grooves of the series formed in the lower face and have each a concavely curved bottom surface, whereby each pair of registering grooves defines in the strip a downwardly arched partition of said elastomeric material; said partition having a thickness amounting to A1 to /2 thickness of the strip, and said longitudinally directed grooves having each a depth amounting to /5 to /3 thickness of the strip.

5. An expansion joint structure comprising: a pair of road sections having a road surface and adjacent end portions enclosing therebetween an expansion gap; a flat road sections having a road surface and adjacent end portions to bridge by its width both said end portions and gap; said strip comprising a substantially planar upper face providing for the continuity of the road surface over said gap, a substantially planar lower face in strip-supporting contact with said end portions of said sections, and a pair of integral beads depending from the longitudinal edges of the strip embedded and anchored in the respective road sections, said longitudinal edges receiving a strip-compressing thrust from the respective road sections on thermal expansion of at least one of said sections and having flanks which are substantially planar and form with the upper face of the strip a dihedral angle of to said lower face of the strip being formed with a pair of grooves directed longitudinally of the strip and adjacent the respective beads whereby the strata of the strip adjacent said lower face are substantially prevented from being compressed by said thrust, and being moreover formed with a series of mutually parallel grooves extending obliquely between said pair of longitudinally directed grooves, the grooves of said series having each a convexly curved bottom surface; and said upper face of the strip being also formed with a series of grooves which are in register with corresponding grooves of the series formed in the lower face and have each a concavely curved bottom surface, whereby each pair of registering grooves defines in the strip a downwardly arched partition of said elastomeric material; said partition having a thickness amounting to /1 to /2 thickness of the strip, and said longitudinally directed grooves having each a depth amounting to /5 to /3 thickness of the strip.

6. An expansion joint structure comprising: a pair of road sections having a road surface and adjacent end portions enclosing therebetween an expansion gap; a flat strip of elastomeric material superposed on said end portions to bridge by its width both said end portions and gap; said strip comprising a substantially planar upper face providing for the continuity of the road surface over said gap, a substantially planar lower face in strip-supporting contact with said end portions of said sections, and a pair of integral beads depending from the longitudinal edges of the strip embedded and anchored in the respective road sections, said longitudinal edges receiving a stripcompressing thrust from the respective road sections on thermal expansion of at least one of said sections; said lower face of the strip being formed with a pair of grooves directed longitudinally of the strip and adjacent the re spective beads whereby the strata of the strip adjacent said lower face are substantially prevented from being compressed by said thrust, and being moreover formed with a series of mutually parallel grooves extending obliquely between said pair of longitudinally directed grooves, the grooves of said series having each a convexly curved bottom surface; and said upper face of the strip being also formed with a series of grooves which are in register with corresponding grooves of the series formed in the lower face and have each a concavely curved bottom surface, whereby each pair of registering grooves defines in the strip a downwardly arched partition of said elastomeric material; said joint moreover comprising a metal blade inserted into each of said beads to longitudinally extend in the latter while protruding downwardly from the bead, means clamping each of the beads on its associated blade throughout the length of the bead, and

a plurality of discrete anchoring members depending from the protruding part of each of the blades, whereby the beads are anchored to their respective end portions of the road sections.

7. An expansion joint structure comprising: a pair of road sections having a road surface and adjacent end portions of concrete defining therebetween an expansion gap; a fiat strip of elastomeric material superposed on said end portions to bridge by its width both said end portions and gap; said strip comprising a substantially planar upper face providing for the continuity of the road surface over said gap, a substantially planar lower face in stripsupporting contact with said end portions of said sections, and a pair of integral beads depending from the longitudinal edges of the strip embedded and anchored in the concrete, saidlongitudinal edges receiving a stripcompressing thrust from the respective road sections on thermal expansion of at least one of said sections; said lower face of the strip being formed with a pair of grooves directed longitudinally of the strip and adjacent the respective beads whereby the strata of the strip adjacent said lower face are substantially prevented from being compressed by said thrust, and being moreover formed with a series of mutually parallel grooves extending obliquely between said pair of longitudinally directed grooves, the grooves of said series having each a convexly curved bottom surface; and said upper face of the strip being also formed with a series of grooves which are in register with corresponding grooves of the series formed in the lower face and have each a concavely curved bottom surface, whereby each pair of registering grooves defines in the strip a downwardly arched partition of said elastomeric material; said joint moreover comprising a metal blade inserted into each of said beads to longitudinally extend in the latter while protruding downwardly from the bead, means clamping each of the beads on its associated blade throughout the length of the bead, anda plurality of discrete anchoring members depending from the protruding part of the blade, in an arrangement wherein both the protruding part of each blade, the clamping means and anchoring members are embedded in the concrete thereby to anchor the beads to their respective road sections.

8. The structure of claim 7, wherein said downwardly arched partition has a thickness amounting to A to /2 thickness of the strip, and wherein said longitudinally directed grooves have each a depth amounting to /s to /3 thickness of the strip,

References Cited UNITED STATES PATENTS 1,982,580 11/1934 Fischer 9418 2,013,195. 9/1935 Ward 1416 2,316,233 4/1943 Fischer 94-18 3,018,703 1/1962 Fujihara 94-18 3,113,493 12/1963 Rinker 94-18 3,165,986 1/1965 Hirst 94-18 3,273,473 9/1966 Pare 94l8 ERNEST R. PURSER, Primary Examiner.

N. C. BYERS, Assistant Examiner. 

7. AN EXPANSION JOINT STRUCTURE COMPRISING: A PAIR OF ROAD SECTIONS HAVING A ROAD SURFACE AND ADJACENT END PORTIONS OF CONCRETE DEFINING THEREBETWEEN AN EXPANSION GAP; A FLAT STRIP OF ELASTOMERIC MATERIAL SUPERPOSED ON SAID END PORTIONS TO BRIDGE BY ITS WIDTH BOTH SAID END PORTIONS AND GAP; SAID STRIP COMPRISING A SUBSTANTIALLY PLANAR UPPER FACE PROVIDING FOR THE CONTINUITY OF THE ROAD SURFACE OVER SAID GAP, A SUBSTANTIALLY PLANAR LOWER FACE IN STRIPSUPPORTING CONTACT WITH SAID END PORTIONS OF SAID SECTIONS, AND A PAIR OF INTEGRAL BEADS DEPENDING FROM THE LONGITUDINAL EDGES OF THE STRIP EMBEDDED AND ANCHORED IN THE CONCRETE, SAID LONGITUDINAL EDGES RECEIVING A STRIPCOMPRESSING THRUST FROM THE RESPECTIVE ROAD SECTIONS ON THERMAL EXPANSION OF AT LEAST ONE OF SAID SECTIONS; SAID LOWER FACE OF THE STRIP BEING FORMED WITH A PAIR OF GROOVES DIRECTED LONGITUDINALLY OF THE STRIP AND ADJACENT THE RESPECTIVE BEADS WHEREBY THE STRATA OF THE STRIP ADJACENT SAID LOWER FACE ARE SUBSTANTIALLY PREVENTED FROM BEING COMPRESSED BY SAID THRUST, AND BEING MOREOVER FORMED WITH A SERIES OF MUTUALLY PARALLEL GROOVES EXTENDING OBLIQUELY BETWEEN SAID PAIR OF LONGITUDINALLY DIRECTED GROOVES, THE GROOVES OF SAID SERIES HAVING EACH A CONVEXLY CURVED BOTTOM SURFACE; AND SAID UPPER FACE OF THE STRIP BEING ALSO FORMED WITH A SERIES OF GROOVES WHICH ARE IN REGISTER WITH CORRESPONDING GROOVES OF THE SERIES FORMED IN THE LOWER FACE AND HAVE EACH A CONCAVELY CURVED BOTTOM SURFACE, WHEREBY EACH PAIR OF REGISTERING GROOVES DEFINES IN THE STRIP A DOWNWARDLY ARCHED PARTITION OF SAID ELASTOMERIC MATERIAL; SAID JOINT MOREOVER COMPRISING A METAL BLADE INSERTED INTO EACH OF SAID BEADS TO LONGITUDINALLY EXTEND IN THE LATTER WHILE PROTRUDING DOWNWARDLY FROM THE BEAD, MEANS CLAMPING EACH OF THE BEADS ON ITS ASSOCIATED BLADE THROUGHOUT THE LENGTH OF THE BEAD, AND A PLURALITY OF DISCRETE ANCHORING MEMBERS DEPENDING FROM THE PROTRUDING PART OF THE BLADE, IN AN ARRANGEMENT WHEREIN BOTH THE PROTRUDING PART OF EACH BLADE, THE CLAMPING MEANS AND ANCHORING MEMBERS ARE EMBEDDED IN THE CONCRETE THEREBY TO ANCHOR THE BEADS TO THEIR RESPECTIVE ROAD SECTIONS. 